Causation in the Law
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Missouri Law Review Volume 73 Issue 2 Spring 2008 Article 6 Spring 2008 Choosing What We Mean by Causation in the Law Jane Stapleton Follow this and additional works at: https://scholarship.law.missouri.edu/mlr Part of the Law Commons Recommended Citation Jane Stapleton, Choosing What We Mean by Causation in the Law, 73 MO. L. REV. (2008) Available at: https://scholarship.law.missouri.edu/mlr/vol73/iss2/6 This Conference is brought to you for free and open access by the Law Journals at University of Missouri School of Law Scholarship Repository. It has been accepted for inclusion in Missouri Law Review by an authorized editor of University of Missouri School of Law Scholarship Repository. For more information, please contact [email protected]. Stapleton: Stapleton: Choosing What We Mean Choosing what we mean by "Causation" in the Law JaneStapleton* In a radical new account of "causation" in the Law, I argue that "causa- tion" is a term we use to express diverse information about the world. Clarity is promoted if we use the term "causation" to refer to the information yielded by only one type of inquiry. Lawyers have used the term to refer to more than one type of enquiry, and philosophers often do not specify an inquiry. The most useful inquiry for legal purposes is one that compares the actual world of a particular phenomenon with a hypothetical world and thereby de- termines, in the context of that comparison, the role that a specified factor played, if any, in the existence of the actual phenomenon. It is convenient to separate three forms of such a role of "involvement": necessity, duplicate necessity and contribution, though contribution subsumes the others. We use our knowledge of the physical laws of nature, evidence of behaviour and so on to distinguish involved factors from factors that are merely "associated" with that phenomenon by a relation of constant conjunction: a determination that can be done objectively. I argue that Law should unequivocally choose involvement as the interrogation underlying causal terminology because (a) it promotes clarity and avoids ambiguity; (b) it promotes the clear identification of normative issues and provides a more transparent distribution of issues between "causation" and other analytical elements within legal analysis; and (c) it best serves the Law's very wide range of purposes. Part I of this article sets out the above argument. Part II sketches the approach of others to the issue of "causation in the Law." I. INVOLVEMENT A. GeneralLaws The world is out there, seamless and rolling along, manifesting what we call the physical laws of nature in complex confluence and combinations. * Professor, the Australian National University College of Law; Ernest E. Smith Professor of Law, University of Texas School of Law. This article is dedicated with the deepest respect to Professor David A. Fischer. With thanks to Judith Jarvis Thomson, Jonathan Schaffer, my seminar students at the University of Texas School of Law and especially to the intellectual generosity of Tony Honord who continues to inspire my interest in causation. A shorter version of this article will appear as a chapter entitled "Causation in the Law," also dedicated to Professor Fischer, in the OXFORD HANDBOOK OF CAUSATION (Helen Beebee, Peter Menzies & Chris Hitchcock eds., Oxford University Press, forthcoming). Published by University of Missouri School of Law Scholarship Repository, 2008 1 Missouri Law Review, Vol. 73, Iss. 2 [2008], Art. 6 MISSOURI LAW REVIEW [Vol. 73 Just as we can deconstruct a particular Van Gogh painting we admire into the three primary colours, so too we can use a variety of limited interrogations to investigate this complex world and discover its underlying building blocks of physical laws.' A well-known example is Newton's First Law of Motion: in an isolated system, an object will maintain a constant velocity unless acted upon by an unbalanced force. We express this latter proposition as a "law" to indicate that it applies (or so it seems on the non-quantum scale) in our natural world. Of course, we can imagine other worlds where this proposition does not hold because, for example, miracles happen or witches cast spells, and we can acknowledge that we do not know why it holds in our natural world,' but these possibilities are not the concern of lawyers who are only concerned with our natural world and hypothetical variants of it in which such physical principles hold. So if we call "medium necessity" the relation that in our natural world (and the hypothetical variants of it in which lawyers are interested) if A does not occur, B also does not occur, 3 Newton's First Law of Motion can be ex- pressed in such terms: in all possible relevant variants of our natural world in which an object has not been acted upon by an unbalanced force, deviation from constant velocity does not occur; or, in all possible relevant variants of our natural world, absence of an unbalanced force is "necessary" for an object to maintain constant velocity. We can also state the First Law in terms of "medium sufficiency": in all possible relevant variants of our natural world, that Y did not occur entails that X did not occur. For example: in all possible relevant variants of our natural world, that deviation from constant velocity did not occur entails (i.e. is sufficient to establish the truth of the proposition) that the object had not been acted upon by an unbalanced force. 1. Scientists deal with the whole seamless world and have described their project as asking: why is it so? (Julius Sumner Miller); what's the go of it? (James Clerk Maxwell); why things are as they are and not otherwise? (Johannes Kepler). Yet, like everyone else, scientists can only make finite interrogations of the world. It is by multiple precisely characterized experiments that scientists achieve an under- standing of how things are in the world, and then express this understanding in terms of physical laws of nature (the origin of which we of course do not know). 2. Richard Feynman, The Character of Physical Law (Modem Library 1994). 3. The term philosophers use for "medium necessity" is "nomological necessi- ty." They distinguish it from "strong necessity" (or "metaphysical necessity"), by which they mean necessity in all imaginable worlds, not just those in which our natu- ral laws apply. On such critical distinctions, see Judith Jarvis Thomson, Some Reflec- tions on Hart and Honorg, Causation in the Law, in THE LEGACY OF H.L.A. HART: LEGAL, POLITICAL, AND MORAL PHILOSOPHY (Matthew Kramer et al. eds., Oxford University Press, forthcoming Sept. 2008). https://scholarship.law.missouri.edu/mlr/vol73/iss2/6 2 Stapleton: Stapleton: Choosing What We Mean 2008] "CAUSATION" IN THE LAW B. Individual Phenomena and Specified Factors Armed with such knowledge of general physical laws and other data such as eyewitness testimony of behaviour, we can investigate a particular individual phenomenon. This phenomenon might, for example, be the actual persistence of a specified state (the cannonball resting on Kant's cushion) or the actual transition from a specified state to another (the fall of the apple from the tree onto Newton's head). Typically our investigations into a particular phenomenon focus on a specified factor - such as a physical force, the absence of something 4 or a specific piece of communicated information. Importantly in the particular context of the Law, the specification of the factor is precise and often arises from what the Law has mandated: if the Law had mandated that Newton's mother should hold an umbrella above her son's head and Mrs. Newton omit- ted to do this, one factor of interest would be this absence, specified as "Mrs. Newton's omission to hold the umbrella as mandated." Often we are interested to compare the actual world of the particular phenomenon (which, of course, includes our specified factor) with a hypo- thetical world (which we construct by notionally omitting the specified factor and sometimes other factors). By doing this we can then determine, in the context of that comparison, the role the specified factor played, if any, in the existence of the actual phenomenon. Importantly in the particular context of the Law, there is often need to consider a hypothetical world, which not only never existed, 5 but which also is one which in retrospect is known could not have existed. An example of such a world is one in which a retailer would have made a $30 profit from a farmer fulfilling a contractual promise to de- liver peas on a certain day... a delivery which turned out to be impossible; in the context of that comparison it is important to understand how it is that lawyers convey meaningful information when they say that the farmer's con- tractual breach "caused" the retailer to suffer a $30 "loss" (see below).6 4. The Law is often engaged in investigating the role of omissions, for example: when a child dies following a parent's neglect; when a lifeguard, in breach of his legal obligation, fails to try to rescue a toddler drowning in the shallows of the surf; or a statute describes torture in terms of the denial of certain support. 5. For example, suppose that all workers in an industry are exposed to a metal dust that triggers a specific cancer. In breach of a duty mandated by the Law, all employers fail to provide the masks that would have prevented the dust being ab- sorbed. One worker, V, contracts the cancer. Pursuing its interest in the involvement of the breach by V's employer, the Law will consider what would have happened in the hypothetical world where V's employer provided masks.